This study seeks to understand the neural, cognitive and behavioral effects of low doses of psilocybin administered in the form of dried mushroom material (0.5 g of Psilocybe cubensis) consumed in natural settings following a placebo-controlled double-blind experimental design.

Sub-threshold doses of serotonergic psychedelics are frequently consumed as cognitive enhancers, and due to their purported positive effects on mood, energy and creativity ("microdosing").

The acute and short-term effects of psilocybin (the psychoactive compound of Psilocybe cubensis mushrooms) on several variables will be investigated, comprising spontaneous and evoked electrophysiological brain activity, perception and cognitive function (cognitive flexibility, attention, inhibitory control, conscious access, visual perception), creativity (problem solving, divergent and convergent thinking), behavior (actigraphy and sleep patterns, natural language production) and several domains related to well-being and mental health of the participants.

This study is simultaneously naturalistic (i.e. recruited subjects are intrinsically motivated to microdose, as they have decided to embark in a microdosing protocol) and controlled by expectations, following a double-blind placebo-controlled design. Participants will microdose according to the following schedule:

Two sessions (0.5 g dried Psilocybin mushrooms vs. dried edible mushroom material without psychoactive effects as a placebo condition) will be conducted. A third party will be in charge of generating their active dose and placebo capsules, and they will also implement a blinding procedure.

Each session will span one week of measurements. Subjects will be given a smartwatch to monitor activity and sleeping patterns at the beginning of the week. At days 3 and 5, subjects will take capsules with active mushroom material or placebo, and then several variables will be recorded. Experiments will be conducted in a setting that is natural and comfortable for the participants, e.g. their homes.

The main outcome measures consist of resting state activity recorded with EEG, evoked response potentials and performance during cognitive tasks, behavioral variables obtained with actigraphy and automated sleep scoring, natural language analysis, and several measurs self-reported via standarized questionnaires.

After completion, this study will provide direct evidence concerning the efficacy of microdosing for cognitive enhancement under natural conditions, i.e. those most frequently used by individuals who microdose, as well as provide information concerning the potential underlying neurobiological mechanisms.

Inclusion Criteria:

1. Men and woman with more than 21 years.
2. Participans are planning to microdose using their own dried mushroom material and adhere to the experimental protocol.
3. No active psychiatric conditions requiring treatment with psychotropic medications.
4. Able to provide informed consent.

Excusion Criteria:

1. Use of psychotropic medication during the study, including stimulants such as caffeine.
2. Prior adverse reactions to psychedelics according to the Challenging Experiences Questionnaire administered during initial screening.
3. Pregnant women or women during lactation
4. History of high or low blood pressure or other cardiovascular risks.

All raw data will be made available online through a data sharing webside (e.g. Zenodo) upon publication of the pre-pring containing the results of our study.

After publication, indefinite.

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